41 lines
1.2 KiB
PHP
41 lines
1.2 KiB
PHP
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; ;;
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;; Copyright (C) KolibriOS team 2004-2017. All rights reserved. ;;
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;; Distributed under terms of the GNU General Public License. ;;
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;; ;;
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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; This crc32 routine doesn't use precomputed table to allow different
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; polynomials, which is the first param.
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; Partial hash in assumed to be eax (both in and out).
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; Usage:
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; 1. mov eax, -1
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; 2. stdcall crypto.crc32 zero or more times
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; 3. xor eax, -1
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proc crc_32 _poly, _buffer, _length
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push ebx ecx edx esi
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mov esi, [_buffer]
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.next_byte:
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dec [_length]
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js .done
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movzx ebx, byte[esi]
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inc esi
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mov ecx, 8
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.next_bit:
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mov edx, eax
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xor edx, ebx
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shr eax, 1
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test edx, 1
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jz @f
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xor eax, [_poly]
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@@:
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shr ebx, 1
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dec ecx
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jnz .next_bit
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jmp .next_byte
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.done:
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pop esi edx ecx ebx
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ret
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endp
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